Process of producing acoustic material



Patented July 20, 1937 UNITED STATES 2,087,550 PROCESS OF PRODUCING ACOUSTIC MATERIAL John A. Rice, Berkeley, Calif., assignor to The Bubblestone Company, Pittsburgh, Pa., a cor poration of Pennsylvania No Drawing. Original application April 27, 1931,

Serial No. 533,351.

Divided and this application October 18, 1935, Serial No. 45,685

2 Claims.

The present application forms a division of my co-pending application for U. S. patent Process and apparatus for making acoustic material and foaming compounds, Ser. No. 533,351 filed April 27, 1931, and in like manner the apparatus em-' ployed for producing or creating the foam constitutes a division of said parent application and is co-pending herewith.

The invention relates to acoustic and/or cellular material and tea process for making acoustic material and/or cellular concrete from materials such as Portland cement, gypsum and other cements, and clay etc., materials which are made plastic with a liquid and thereafter iven a 'cel- 15 lular structure -by introducing cells gas, and

thereafter being hardened, retaining the cellular structure and foaming compounds used therein. The invention relates to foaming compounds as used in combination with Portland cement, or other cements, or clay, etc., air and water, with or without other aggregate than air, to form cellular concrete. More particularly my improvements relate to foaming compounds which are suitable to be used in forming cellular mixtures 25 of cement, clay, etc., water and air by means of agitation or by forcing air into slurry made of cement or clay etc., which hasbeen prepared by introducing a proper amount of foaming compound. However, these improved compounds 30 when diluted with water may be also used to form a suitable foam, which may subsequently be mixed with cement slurry and the like, forming cellular concrete.

Heretofore many of the existing materials and 35 methods of making foaming compounds used for the purposes stated have not provedwholls satisfactory in commercial operation, for several reasons:-

First, they were not in suitable concentrated to forms for transporting long distances and thereafter diluting with water or other cheap diluent to make them ready for use.

Second, their chemical condition was not stable, so that upon transporting and after a lapse of time, or upon long storage, the eiliciencyand characteristics of the compounds might change adversely, due to said chemical instability,

Third, their eiliciency in general was inadequate, so that it was dlfficult to make proper 50 thick, viscid cellular mortar with cement and a satisfactorily small amount of the foaming compound. The invention which may be manufactured in large quantities,

55 which have uniform'foaming characteristics, and

structure eilectively and efficiently without chemrelates to foaming compounds water or other liquid. In place of the artificial which are adapted to associatewith Portland cement, gypsum and other cements, or clay and the like without impairing the ultimate strength of. th resulting cellular concrete; which have the quality of preserving the .form of the .voids or spherical cells unimpaired during the settin of the cement or drying of the clay or the like and which are in a concentrated liquid state suit able for shipment and storage and thereafter capable of dilution as much as desired with suitable solvents. The improved compounds will keep indefinitely without adverse chemical change, that is to say they are chemically stable. The compounds are eflicient as foaming compounds in the presence of calcium hydrate and other sub-' stances contained in or produced by Portland cement during hydration of the same.

My discoveries relate to the foaming nature of soluble condensation products of phenols and al- .dehydes, and to rosin and related soluble resinous substances, when mixed with cement or clay or the like, and water. I have discovered that when condensation products of phenols and aldehyde's are dissolved in water by means of suitable solvents and mixed with slurry made with cement or clay or the like, the substances are precipitated in the form of a voluminous colloidal foamy body which remains stable during agitation and aeration and during subsequent hours while the cement is. setting, holding the cellular icalhr changing or injuring the nature of the cement with respect to its ultimate structural strength.

My invention further comprises physical methods of rupturing the walls of the cells in materials of cellular structure thereby forming continuous pore structure in such materials, thus especially adapting the same to be used for acoustic or non-sound reflecting surfaces, as on the walls and ceilings of auditoriums and the like.

Generally stated, my invention comprises the use of stable foaming agents, consisting of resins formed from, a phenol and an aldehyde, .or from an aldehyde or aldehydes, the phenol being either phenol proper or cresol (cresylic acid) or a material of similar chemical nature and the aldehyde being ordinary aldehyde, formaldehyde, furfural, or other aldehyde, all of these being used in association with cements of various kinds including Portland cement, gypsum cement, clay; kieselguhr, bentonite, or other powdered material which will se or solidify by chemical action or by dryingafter having been made plastic with resins formed by the condensation of a'phenol or the likewith an aldehyde, the invention also includes the use of hydrated metallic oxids in combination with the above materials, particularly the hydrated oxids of chromium, titanium and aluminum. In place of the synthetic resins mentioned, the invention also includes the use of rosin.

The invention pertains further to a method of making acoustic material by aerating a mixture of cement and water containing a-suitable foaming agent, and thereupon allowing the material Parts by volume Phenol 200 Formalin 100 Potassium hydroxid (water solution 40 degrees B.) 10

Heat gradually, boiling until the temperature reaches 212 degrees F. Cool at once.

The resulting compound will be a resinous product.

I(b) to I(a) after cooling, add potassium hy-, droxid solution until, upon dropping a small amount in water, it is seen to be entirely soluble in water.

I(e) to I(b) add sufficient water to dilute the soluble resin to the consistency of molasses. This will require about 80 parts of water, more or less,-

according to the degree of concentration resulting from evaporation of water. The resulting soluble resin solution should have a specific gravity of about 20 to 22 degrees B.

I(d) For use as a foaming compound in the making of cellular concrete, I(c) should be diluted with water as follows:

. Parts by weight I(c) 100 Water 600 and used in the approximate proportion of two pounds to the cubic yard of cellular concrete product.

I(e) Instead of using potassium hydroxid to render the resin soluble in water and then using water for the diluting medium, alcohol may be used to dilute the resin as prepared under I(a) In such a case take Parts by weight Resin I(a) 100 Alcohol approximately 900 and use in the approximate proportion of two pounds to the cubic yard of cellular concrete product.

11(0), Mix together Parts by volume Commercial cresylic acid (cresol) 20o Formaldehyde (40%) 70 Potassium hydroxid 40 deg. Be 10' Heat in a suitable container till the mixture has reached 220 degrees F. This will produce a resinous condensation product.

-II(b) After cooling the resin 1101) add suflicient additional potassium hydroxid solution to render the resin soluble in water. sufllcient additional water to bring the specific gravity to 20 to 22 degrees B. so that the resin solution becomes sufliciently liquid to be conveniently handled in containers.

11(0) For use as a foaming compound in the manufacture of cellular concrete, take of,

' 1 Parts by weight II(b) 100 Water 600 and thoroughly mix together, dissolving the resin solution in the water. Use 2 pounds to the cubic yard of cellular concrete product.

. II(d) Instead of using potassium hydroxid to render the resin solution soluble in water, alcohol may be used as a solvent as follows:-

Parts by weight Resin solution 11(0) 100 Alcohol 900 III( Mix together Parts by volume Commercial cresylic acid 200 Commercial furfural 70 Potassium hydroxid sol. 40 deg. B 10 Heat gradually to a temperature of 240 degrees F. This will produce a resinous condensation product.

may) to mun add sufficient potassium hydroxid solution to render the resin solution completely soluble in water and finally add sufiicient Then add water to bring the specific gravity to 20 to 22 degrees B. for the purpose of convenience and standardization of strength.

III(c) For use as a foaming compound in the Parts by weight III(b) 100 Water -1. 600

and use two poundsof the same to each cubic yard of cellular concrete to be made.

III(d) Using alcohol as a solvent for the resin,

-malri ng of cellular concrete dilute as follows:

take

Parts by weight III(m) 100' Alcohol 900 After solution is. complete this compound may be used in the proportion of two pounds of the compound to the cubic yard of cellular concrete to be manufactured.

IV(G) Bakelite A" liquid resin may be used by adding suflicient alkaline solvent to render it soluble in water and diluting with water to the standard diluti.on,20 to 22 degrees B.

IV(b) For use as a foaming compound in the making of cellular concrete, dilute as follows:

Parts by weight IV(d) 100 Water 600 This solution may be then used as directed under III(c).

IV(c) Alcohol may be used as a solvent instead of the potassium hydroxid as follows:

Parts by weight IV(a) 100 Alcohol 900 This alcohol solution then may be used as directed under I[I(c).

Ethyl or methyl alcohol and potassium, so-

dium or other alkaline hydroxids may be used in the above formulas.

V(a) Rosin (colophony) may be used as a foaming agent. A suitable compound for use in making cellular concrete may be made as follows:

Powdered rosin 100 -Water 1000 Ammonia (approx.) 60

The mixture may be heated to facilitate saponiflcation. Enough ammonia should be added so that there is a distinct ammonia odor apparent after all the rosin has been saponifled Hie amount may be somewhat more or less than the 1 V,(c) Rosin dissolved in alcohol may be used. Mix

Parts by weight 100 900 V(d) Esterifled rosin prepared in the manner well known to varnish manufacturers may be used in the same way as directed in the case of Powdered rosi Alrnh 01 plain rosin.

VI(a) Aldehyde resins, other than phenolicaldehyde resins, also may be used as foaming compounds for use with cements in making cellular concrete. For example:

Mix together Parts by volume Furfural (an aldehyde) .;.100 Water 300 Potassium hydroxid sol. 45 degrees B 100 Carefully heat the mixture to 212 degrees F.,.

stirring meanwhile. A highly colored red condensation product will result.

VI(b) Dilute VI(a) as follows:

, Parts by weight VIM) 100 Water 200 when using the above formulae it is advisable to use the specific dilution given, for reasons of economy. However, the resin and rosin solutions, if sufliciently liquid, may be diluted over av -wide range of concentrations-that is to say,

little or much diluent may be used and the resultant foaminess of the compound may be satisfactory, provided a longer time of agitation be given in the case of highly diluted solutions. For'reasons of economy it is well to use a minimum amount of the resins, and on the other hand, for reasons of efliciency it is well to avoid Parts by weight too high a dilution of the same.

considerations that the above concentrations are given as preferable.

It is forthese 1 I g In thecase of using an alcohol as a solvent,

suflicient dilution of. the resin, or rosin, should be. obtained, so that when the alcoholic solution is added to clear water. the resin or rosin will precipitate as a finely divided, (practically colloidal), precipitate. If the solution be too concentrated, the resin or rosin will precipitate in globules and will not disseminate homogeneously throughout the water, and will quickly settle to the bottom of the vessel instead of remaining [in suspension as is to be desired.

" Various substances may. be used to advantage as modifying agents in association with the Ford-nstance some hydrated metallic oxids will give body to thefoamy substances produced, and

several such substances have the advantageous oxid. These may be incorporated with the resinuous compounds as shown below.

" Parts by weight VII(a) Chromium acetate; 100

Water 600 Parts by weight VII(b) Titanium sulphate cake 100 Water.

J Parts by weight VIlI(a) 1(0) or 11(b) or III(b) or IV(a) 100 Potasslum hydroxid sol. 45 deg. 31%.. 52 Water 600 VII(a) 30 If this solution does not become clear after stirring a few minutes. additional potassium hydroxid solution should be added. More or less of the chromium salt solution than designated may be used if desired. provided that a suitable amount of potassium hydroxid is used to neutralize the acetic acid and to dissolve the resulting hydrated chroniium cxid. The solution VIlI(a) may now be used as a foaming. compound for making cellular concrete, using two pounds, more or less,;o f the same to each cubic yard of product. The greater the quantity used the more quickly will the'foamy batch become thick. The cement cellular product will harden better and attain greater-ultimate strength because .of thehydrated chromium oxid.

' 7 Parts by weight IV(a) 100 600 Parts by weight IX(b) V1102) the titanium mixture 50 Water 50 Parts by weight IX(c) Take of'IX(a) 700 Take of IX(b)' 100 rxm) 110:) or not) or man Water containing disseminated should then be treated in a colloid mill to break up the clots and to render the mixture homogeneous: Add sufllcient calcium hydroxide, (in powdered form), to precipitate the sulfur as calcium sulfate. This amount will approximate fifteen parts by weight but should be closely determined by usual methods of testing. The mixture 12(0) may then be used as a foaming comresinous. compounds used for the purpose given.

' additional films being formed with air entrapped pound for the manufacture of cellular concrete by using two pounds of the same to the cubic yard of cellular concrete to be made. More or less may be used, as stated for the other compounds mentioned. The cement product will harden better and attain a greater ultimate strength because of the hydrated titanium oxid present.

The various foaming compounds described above may be used in a suitable machine such as disclosed in my co-pendlng application Ser. No. 45,684 filed October 18, 1935, or may be used to make a foam which may then be combined with a suitable cement slurry. I prefer to combine-the cement slurry and foaming compound before aerating, and to .then aerate the mixture in the special and improved machine.

Continued operation of the machine will finally use up the available water of the slurry, forming air cells each with a surrounding film of water containing a minute quantity of foaming compound. Thushthe aeration will cease when no more water is available, and the slurry will cease to expand in volume as a consequence. If more water is added and the machine operated, then the slurry will further increase in volume due to therein.

A suitable mixture is as follows:

Water gallons 8.5 Sand (finer than 50 mesh to v the inch) cubic foot 1 Cement pounds (1 sack) 94 Foaming compound ounce s 7 (Sand should be finer than 50 mesh and coarser than 100 mesh) When aerated, this mixture will have a volume of approximately six cubic feet, weighing approxof the structure. Upon hardening, the surface.

of the cellular concrete may be smoothed off to a plane surface by means of a rubbing stone-or other appliance, when the porosity of the concrete will prove to be such that air may be blown through the material, or water will flow through it by gravity. Such a structure is efficient as a nonreflecting surface with respect to sound, and material of this'sort may be used as an acoustic surface for walls ofauditoriums and the like;

My experiments relating to physically rupturing the cell walls were made with specimens of Bubblestone, a material made from Portland cement, and sand and containing numerous voids or cells, (spherical), of air such that the speci- -mens were much lighter than pieces of stone or concrete of the same size would be.

In preparing the specimens for the experiments the following procedure was employed:

(1) The cement, water and sand, (of a fineness passing 50 meshesto the inch but retained on 100 meshes to the inch), were mixed, forminga thick slurry; equal proportions of cement and sand were used;

(2) A small amount of Bubblestone foam compound was diluted with water and beaten to a stiff foam; I

(3) A sufficient amount of the foam (2) was thoroughly mixed with the cement slurry (1), to form a plastic cellular concrete of the desired weight, (in this case approximately 30 pounds to the cubic foot). Of course it is obvious that a less proportion of foam would form a heavier product and that a greater proportion of foam would form a lighter product.

The experiment was carried out by placing the plastic cellular concrete in a suitable mold, and the mold containing the cellular concrete was then placed in an air tight container having suitable strength and provided with means for applying air pressure, and means for applying a partial vacuum, and maintaining a pressure or vacuum as long as desired. Upon closing the container, air pressure was applied to the extent of approximately one-half atmosphere,that is to say, sufficient pressure was applied to support a column of mercury having a height of 16 inches and the mold in its container was allowed to stand until the cellular concrete had set" sufficiently to maintain its structure when the air cells might be ruptured. The time allowed was twelve hours with the temperature at 65 degrees F. (With a higher temperature or with an accelerator in the mix this proper time might be less,

. or with a lower temperature it might be greater.)

After 12 hours the pressure was released slowly. This releasing of the air pressure around the mold containing the cellular concrete resulted'in expansion of the air within the spherical cells of the cellular concrete with a consequent rupture of the walls of the cells or voids, accomplishing the desired result. Thereafter the mold was set aside a timesuflicient to allow the cement to harden, to give the desired strength to the specimen. T'hereupon 'the surface of the specimen was planed off by rubbing with a carborundum brick to give the desired plane surface. It was found to have a freely porous structure such that water would flow freely through it or air could be freely blown through it.

In using the above described method, the physical conditions essential for success in breaking down the cell walls of a closed and impermeable'cellular structure such aspumice, substantially hardened Bubblestone", or cellular slag, or similar materials, are:

First, a difference of pressure between the interior of the cells and the outside atmosphere such that the walls of the cells will be ruptured, the air escaping to the atmosphere. Preferably the higher pressure should be within the cells and the lesser pressure without, but the reverse of such condition, if the pressure be sufficient, will also attain the desired result.

Specimens of hardened cellular concrete were placed in the closed container and a pressure applied, amounting to about sixty pounds to the square inch. After allowing them to stand un-- der pressure for a few minutes, the pressure was released. These specimens were found to have been made porous by the breaking down of cell walls. With sufllcient pressure, pumice stone may be rendered porous in the same manner.

,While I have considered clay herein to be a plastic material when the same isaerated. nevertheless, ,after it has been formed into cellular material and dried, calcination of such material is obviously the means of making it hard, strong and nonplastic,--a condition in which it will not be made soft or plastic again even if wetted with water. It is at this stage that the pressure method of breaking the cell walls, for forming acoustic material, isbest made use of.

When treating weak or substantially hardened cellular concrete as described herein, it will be simpler to use a partial vacuum instead of pressure, as follows:

The plastic cellular concrete may be cast in the molds at atmospheric pressure and allowed to stand until it has reached the desired stage of setting. It may thenibe-placed in themtight container and vacuum applied to a sufficient degree, that is, to approximately half an atmosphere, more or less, according to stiffness of the concrete. Atmospheric pressure may be then restored and the mold removed. The exhaustion of the air in the chamber will produce a difference of pressure between the interior of the cells and the outside, resulting in the rupture of the cell walls as before. Hydraulic pressure may be used as well aspneumatic pressure, when treating hardened material such as pumice.

It will be understood that inasmuch as this case is a division of application Serial No; 533,351, any of the chemical mixtures employed as foaming compounds and the like therein may be employed in making the cellular material'disclosed herein and such'prior disclosure is to be considered as embodied herein as far as it is applicable -to the acoustic product and the manufacture thereof.

While I. have described above certain materials and processes which are particularly suitable for carrying out my invention, it is obvious that modifications may be made in the processes and materials without departing from the substance of the invention. Therefore, my invention is not to be considered as limited to the specific disclosures in the present specification,

but only as defined in the following claims:

What is claimed as new is:

1. The process of producing an acoustic material which comprises aerating a mixture of cementand water with av suitable foaming agent, and after'partial setting of said mixture, causing cell walls of said material to become ruptured, by applying a vacuum to the material.

2. The process of producing an acoustic material which comprises aerating a mixture of cement and water with a suitable foaming agent, and after partial setting of said mixture, causing cell wallsof said material to become ruptured, by applying pressure and vacuum to the material in any desired sequence.

JOHN A. R ca. 

